1. Field of the Invention
The present invention relates to a method of manufacturing a high-k gate dielectric, characterized in that an annealing process in a forming gas atmosphere, corresponding to a final step of a manufacturing process of a semiconductor device based on fabrication techniques of MOSFET (Metal-Oxide-Silicon Field Effect Transistor), is applied for a semiconductor device having a high-k gate dielectric, under conditions of high concentration (100%) and high pressure, instead of conventional conditions of low concentration (3-5%) and atmospheric pressure, whereby interface charges and fixed charges of the semiconductor device can be maximally passivated even at relatively low temperatures.
2. Description of the Related Art
In general, a manufacturing method of a semiconductor device, which uses silica (SiO2) as a gate dielectric, includes metallization, followed by annealing at about 400450° C. for 10-30 min in a forming gas atmosphere containing about 3-4% hydrogen. In such cases, the annealing treatment functions to allow interface charges existing on an interface of the gate dielectric to be passivated by hydrogen. Thereby, the interface state density is decreased to about 1011/cm2-eV or less, thus ensuring superior charge mobility of the device.
On the other hand, a high-k gate dielectric has much higher interface charges and fixed charges (about 10-1000 times or more) before the annealing treatment, compared to those of silica. Thus, there is required an annealing treatment in a hydrogen atmosphere of relatively high concentrations and high temperatures. In this regard, Jack Lee, Professor, University of Texas, Austin, USA, published a paper (p. 613) on IEDM in December 2002, the paper concerning a method of improving interface charge properties of a high-k gate dielectric composed of forming a high-k gate dielectric, which is then annealed at high temperatures of about 600-700° C. in about 4% hydrogen/deuterium atmosphere, followed by metallization.
At this time, the reason why the high-temperature annealing is performed before the metallization is that the process temperature cannot be increased to 450° C. or more after the metallization, due to the relatively low melting point of aluminum. Further, since 5% or more hydrogen is explosive, the use of hydrogen with a low concentration of 4% or less is preferable for annealing under atmospheric pressure.
However, the above mentioned method has the following drawbacks.
First, although the high-temperature annealing process using forming gas, which is applied for the high-k gate dielectric before the metallization, can passivate interface/fixed charges, it leads to increased effective thickness of the dielectric, and deteriorated leakage current properties due to crystallization. Hence, this process should be performed at relatively low temperatures.
Second, even though passivation is achieved before the metallization, the metallization may cause plasma damage, thereby increasing interface charges over again. Accordingly, it is more preferable that the interface of the high-k gate dielectric is subjected to passivation at low temperatures after the metallization.